I agree with you on the practical impossibility of parting the main cables. I don't remember the exact numbers of wires. The 24.5 dia cable is made up of wires anout #9 siae. that is about 1/8 " dia. I think we made 24 strands each about 3" dia and we coated each strand with red lead paste which would probably resist the acid you are talking about. Then we had a machine we called the compacter to compress all the strandstightly together and then we smeared more red lead paste on the 24.5 " compacted cable and then we hada machine to wrap the whole thing round with wire wound around it and painted it. the individual wires are galvanized hard steel like spring steel. This dense 24.5" dia cable would resist most anything like acid or thermite or explosive. Andeven if half the cross section were cut it would still hold the span up unless a solid line of heavy trucks were on the roadway. So I agree it would be very unlikely to demolish the bridge /
Thank you very much. Enough said.
The more I learn the more impressed I am and really really looking forward to the trip. Its neat getting to read the posts of someone who was involved in building the Mackinac Bridge.